Silicon wafers used in electronic devices are typically prepared from a single crystal silicon ingot that is first sliced into thin wafers using a diamond saw and then ground to remove surface imperfections arising from the sawing process. The silicon wafers thereafter typically require a final polishing step to provide surfaces having very low surface roughness before the silicon wafers are acceptable for use in electronic devices.
Current methods of performing the final polishing of silicon wafers often employ polishing compositions that contain silica as an abrasive in an aqueous carrier and further comprising additives such as amines or quaternary ammonium salts as polishing rate enhancers. Conventional polishing compositions for silicon wafers generally require over 10 minutes of polishing in order to remove 10-20 microns of silica.
Polishing compositions are desired that can be used to polish silicon more quickly to improve throughput and more effectively utilize production capacity. It is well known to use amines in silicon slurries to increase the removal rate. However, the use of amines in polishing slurries is accompanied by an increase in particle defects and haze on the substrate. Further, in view of environmental concerns such as waste water treatment regulations, the use of amine additives are undesirable.
Thus, there is a need in the art for improved chemical-mechanical polishing compositions exhibiting a high removal rate, low particle defects, and low haze.